Co-doped Y2O3 optical functional nanoparticles and novel self-assembly squama-like aggregates

Co-doped Y2O3 optical functional nanoparticles with size of 4–10 nm have been synthesized by the plasma arc-discharge method. Meanwhile, novel three-dimensional squama-like macro-aggregates were self-assembled by disordered nanoparticles synthesized simultaneously in the arc-discharge process. The formation mechanism of the aggregates is ascribed to the periodic coagulation of Y nanoparticles. The valence states of Co in Y2O3 lattice can be determined as +2 from XPS spectrum with an etching depth of 6 nm. For Co-doped Y2O3 nanoparticles, upon excitation with 426 nm, a red emission (620 nm) has been observed which originates from 4A2(4F) → 4T1(4P) d–d transitions of Co2+ ions in tetrahedral co-ordination.